Wooden pallets have for many years been the primary method for unitizing freight for mechanical handling during shipment and storage. While they are effective for this purpose and reasonable in cost, they nevertheless present significant problems with respect to compliance with many shipping and environmental regulations. For example OSHA regulations state that a person should not lift over 50 pounds, but most wooden pallets weigh on the order of 65-80 pounds. Moreover, when they are stored outdoors they tend to pick up even more weight by adsorption of water. In addition, many countries require that wooden pallets be fumigated before entry.
In addition, wooden pallets create a space problem when shipping and storage space are critical because they cannot usually be disassembled for reuse and their typical thickness of six to nine inches causes a substantial reduction in useful capacity.
Wooden pallets also present a substantial safety and sanitation problem. A major safety problem is flammability of the wood from which they are made. Thus, wooden pallets in storage can create an intense fire if they are ignited which, in some circumstances, may be sufficient to overwhelm conventional sprinkler systems. Also, wooden pallets often have sharp edges, splinters and protruding nails which tend to damage product and frequently cause injury to personnel handling the pallets.
Wooden pallets too often become a health problem because they become infested with insects, birds and rodents. Moreover, because they can't be cleaned effectively with steam, they are subject to mildew and mold contamination. In addition, wooden pallets degrade rapidly in normal atmospheric exposure. Therefore, they can be reused only limitedly.
Structurally, wooden pallets suffer from other disadvantages. For example, conventional wooden pallet construction (see FIG. 8) does not allow four-way entry. They also have sharp edges and nails which are likely to damage product packaging, thus, requiring the use of cardboard covers (slip sheets). As mentioned above, a serious disadvantage is that they cannot be disassembled for volume reduction when they are shipped for reuse.
While it has been proposed that some of the disadvantages of wood pallet construction might be eliminated by the use of plastics, such attempts have been less economical than wood. For example, to make a monolithic molded pallet would involve a very high cost for making the mold. Furthermore, a one-piece pallet of this type could not be disassembled for reuse.
Recent efforts in this regard are illustrated by the following listed prior art patents, which are summarized below: